This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-334958 filed Oct. 31, 2001.
The present invention relates to a reduction type starter having a reduction device, which transmits rotation of a motor to an output shaft in a reduced rotation speeds.
A reduction-type starter is disclosed in U.S. Pat. No. 6,097,119 (JP-A-2000-297729). This starter has a planetary gear reduction device, through which a motor rotation shaft and an output shaft are arranged coaxially to each other. A one-way clutch is helical-spline fit on the outer periphery of the output shaft. The one-way clutch is movable in the axial direction. When an engine is started, the one-way clutch is pushed forward axially together with a pinion gear by using attraction of a magnetic switch until the pinion gear comes to mesh with a ring gear of an internal combustion engine and transmit the rotational force to the ring gear.
However, the starter has an opening at the nose of a housing covering the outer periphery of the pinion gear from which the pinion gear is exposed to engage with the ring gear. As a result, foreign substances (such as water, dust and the like) enter the housing from the opening and adhere onto the bearing surface of a bearing for holding the output shaft arranged in proximity to the reduction device. Thus, it causes loss in rotation and lowering of starter performance.
In addition, shortage of lubricant in the bearing causes lowering of starter performance. When the output shaft rotates, lubricant is discharged from the inside of the bearing onto the bearing surface so as to maintain smooth rotation of the output shaft. But if the starter is operated very frequently, the bearing is likely to run short of lubricant rapidly because the bearing cannot hold much lubricant. As a result, it causes lowering of starter performance.
It is therefore an object of the present invention to provide a starter, which prevents foreign substances from entering into the bearing surface of a bearing and maintains bearing performance for a long time.
According to the present invention, a starter has a bearing for holding an output shaft in proximity to a reduction device and a seal member in sliding contact with the outer periphery of the output shaft in proximity to the front side of the bearing, that is, to the side opposite the motor. The seal member prevents the entering of foreign substances into the bearing surface of the bearing and also limits the flowing out of lubricant held in the bearing. As a result, the bearing maintains high performance for a long time and lowering of starter performance is minimized.
A housing of the starter has a holding part for holding the bearing. A groove is formed annularly or in the ring-shape in the inner peripheral surface of the holding part. The bearing has a plurality of through holes, which pass in the radial direction between the inner surface and the outer surface. The through holes are communicated with the groove. The groove is filled with lubricant in advance. As the lubricant is provided from the groove to the bearing surface of the bearing by the through holes, shortage of lubricant in the bearing is prevented. As a result, even if the quantity of lubricant held at the bearing is small, the bearing maintains high performance for a long time and lowering of starter performance is minimized.
The bearing also has a plurality of recesses on the inner surface thereof. As the lubricant is held in the recesses of the bearing in advance, shortage of lubricant in the bearing is inhibited. Moreover, the housing of the starter has channels to lead the lubricant which flows out of the reduction device to the bearing. When the bearing runs short of lubricant, the recesses of the bearing are refilled with the lubricant which is led to the bearing by the channels. Thus, lubricant is used efficiently.